/*-------------------------------------------------------------------------
 *
 * itemid.h--
 *    Standard POSTGRES buffer page item identifier definitions.
 *
 *
 * Copyright (c) 1994, Regents of the University of California
 *
 * $Id: itemid.h,v 1.1 1996/08/28 01:58:08 scrappy Exp $
 *
 *-------------------------------------------------------------------------
 */
#ifndef	ITEMID_H
#define ITEMID_H

typedef uint16	ItemOffset;
typedef uint16	ItemLength;

typedef bits16	ItemIdFlags;



typedef struct ItemIdData {		/* line pointers */
	unsigned	lp_off:13,	/* offset to find tup */
					/* can be reduced by 2 if necc. */
			lp_flags:6,	/* flags on tuple */
			lp_len:13;	/* length of tuple */
} ItemIdData;

typedef struct ItemIdData	*ItemId;

#ifndef	LP_USED
#define LP_USED		0x01	/* this line pointer is being used */
#endif

/* ----------------
 *	support macros
 * ----------------
 */
/* 
 *	ItemIdGetLength
 */
#define ItemIdGetLength(itemId) \
   ((itemId)->lp_len)

/* 
 *	ItemIdGetOffset
 */
#define ItemIdGetOffset(itemId) \
   ((itemId)->lp_off)

/* 
 *	ItemIdGetFlags
 */
#define ItemIdGetFlags(itemId) \
   ((itemId)->lp_flags)

/*
 * ItemIdIsValid --
 *	True iff disk item identifier is valid.
 */
#define	ItemIdIsValid(itemId)	PointerIsValid(itemId)

/*
 * ItemIdIsUsed --
 *	True iff disk item identifier is in use.
 *
 * Note:
 *	Assumes disk item identifier is valid.
 */
#define ItemIdIsUsed(itemId) \
    (AssertMacro(ItemIdIsValid(itemId)) ? \
     (bool) (((itemId)->lp_flags & LP_USED) != 0) : false)

#endif	/* ITEMID_H */
